The present invention relates to a device for checking decimal data in a data processing system.
A conventional decimal data checking device, as shown in FIG. 1, comprises a main storage command register 1 for storing various commands such, for example, as a read/write command or the like, a command analyzing circuit 2 for analyzing these commands, a data register 4 for storing the data read from the main storage unit and a circuit 3 for checking the decimal format of the data supplied from the data register 4. In the known circuit, the command from the main storage command register 1 is analyzed in the command analyzing circuit 2 and the data necessary for a desirable arithmetic operation are sent via a system bus 7 to the data register 4 .
Upon execution of a desired arithmetic operation, necessary data are read out from the data register 4 to check in the decimal data format checking circuit 3. If no format error is found in the checking operation, then the data are used for the arithmetic operation conducted in the arithmetic operation unit 5 using those data. However, if there is any format error or the like in the data, then, as an exceptional processing, the data are read again into the data register 4 via the system bus 7.
As described above, in the conventional decimal data checking device, the data read from the main storage unit is read into the data register once before the necessary data is checked in the decimal data format checking circuit 3. If there is no error in it, then an arithmetic operation is carried out in the arithmetic operation unit 5 and, if yes, then it is not carried out. In consequence, when the arithmetic operation is done, the quality of the data format which is read from the data register 4 cannot be determined. This means that, prior to the arithmetic operation, it is necessary to arithmetically operate after it is confirmed in the decimal data format checking circuit 3 that there is no error in the decimal data format checking circuit 3, which can delay the processing speed until the arithmetic operation is actually conducted after the data necessary for the arithmetic operation is read out.